Field of the Invention
This invention describes borated overbased materials which are useful in lubricating oils.
It has long been desirable to include boron in a suitable form in a lubricating oil such as for a motor vehicle. Borate salts are highly water soluble materials which tend to partition upon exposure to water, either in storage or in use. It is desirable to minimize such loss or inactivation of the boron in the product. Typically, the boron is incorporated as a portion of an organic molecule or associated with an organic molecule in an attempt to stabilize the borates against water.
The use of boron in a lubricant is to provide proper anti-oxidant, anti-rust, frictional characteristics and extreme pressure qualities to the lubricating oil. The boron typically functions by forming a barrier between moving metal parts through a chemical attraction to the surface of one or both of the metals. It is desirable that the boron be dispersed as much as is possible in the product to ensure that all of the metal surfaces which come in contact with the lubricating oil will be properly protected. This invention deals with the method of obtaining the boron in an organic molecule in extremely small particle sizes such that the boron is substantially distributed at all times throughout the lubricating oil.
It is known from U.S. Pat. No. 3,929,650 to King et al issued Dec. 30, 1975 that alkali metal borates may be prepared by contacting boric acid with an alkali metal carbonate overbased metal sulfonate within an oleophilic liquid reaction medium. It is also known from King et al in U.S. Pat. No. 3,907,691, issued Sept. 23, 1975 that mixed metal borates may be obtained by reacting boric acid with an alkaline earth metal carbonate overbased metal sulfonate in a lubricating oil or grease medium to form an intermediate and thereafter to react alkali metal base with the intermediate to form a mixed alkali and alkaline earth metal borate dispersion.
Hellmuth, in U.S. Pat. No. 3,679,584, issued July 25, 1972 describes a process for increasing the alkaline earth metal ratio of an alkaline earth metal carbonate overbased alkaline earth metal sulfonate lubricating oil composition by introducing into a lubricating oil medium containing a colloidal-like dispersion of an alkaline earth metal carbonate overbased alkaline earth metal sulfonate, an alkaline earth metal hydroxide, and boric acid and subsequently contacting the resultant mixture with carbon dioxide. In U.S. Pat. No. 3,846,313, issued Nov. 5, 1974 to Sims, it is disclosed that particulate hydrated alkali metal borate may be combined with an aliphatic hydrocarbon alcohol and to disperse this mixture in an oil of lubricating viscosity.
Adams, in U.S. Pat. No. 4,100,080, issued July 11, 1978 describes greases which contain organic grease thickeners and dispersions of finely divided borates as extreme-pressure agents. LeSuer in U.S. Pat. No. 3,829,381 issued Aug. 13, 1974, describes borated calcium overbased products.
It is therefore, desirable to obtain a very fine particle size organic source of boron which may be easily dispersed in a lubricating oil or grease. The product should also be formulated to contain a relatively high percentage of carbon dioxide to promote dispersibility of the organic boron source within the product.
The process for obtaining the product of the invention should be conducted such that the substantial foaming upon incorporation of the boron component is avoided. The product should also be obtained conveniently by avoiding alternatively raising and lowering the temperature during the reaction process.
The aforementioned goals are met by producing a product as described herein. Throughout the specification and claims, percentages and ratios are by weight, temperature are in degrees Celsius, and pressures are in KPa gauge unless otherwise indicated. To the extent that the references cited herein are applicable to the present invention, they are incorporated by reference herein.